SOLUTION: One computer need to 75 hours to solve a complicated problem , but a better computer needs 50 hours to solve the same problem .if both computers work in parallel,how much time wil

Algebra ->  Rate-of-work-word-problems -> SOLUTION: One computer need to 75 hours to solve a complicated problem , but a better computer needs 50 hours to solve the same problem .if both computers work in parallel,how much time wil      Log On


   

Question 1035505: One computer need to 75 hours to solve a complicated problem , but a better computer needs 50 hours to solve the same problem .if both computers work in parallel,how much time will be Required to solve the problem?
Answer by ikleyn(52811) About Me  (Show Source):
You can put this solution on YOUR website!
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It is very naive point of view that the rates of two computers can be added.

As a rule, the sum of their rates is not the rate of the parallel system.

The condition is not adequate to real situation.

Formal solution is as this:

1%2F50+%2B+1%2F75 = 3%2F150+%2B+2%2F150 = 5%2F150 = 1%2F30 of the job-per-hour is their combined rate.

Hence, it will take 30 hours for the parallel system to complete the work.

See the lesson Using Fractions to solve word problems on joint work and associated with it for solutions of joint-work word problems.